Method for loading and unloading vehicles



June 1, 1965 A. SPINANGER ETAL 3,136,568

METHOD FOR LOADING AND UNLOADING VEHICLES Original Filegi July 10. 19654 Sheets-Shem l INVENTORS ARTHUR Spmmessz m Eossszr V BURT,

ATTO

June 1965' A. SPINANGER ETAL 3,

METHOD FOR LOADING AND UNLOADING VEHICLES Original Filed July 10, 1963 4sh t -sheet 2 Q g s 3 FR v a;

INVENTOR. Aamua Swmmem mo Roasm' V. B RT,

1m BY f,

ATTORNEY.

June 1, 1965 A. SPINANGER ETAL 3,186,568

METHOD FOR LOADING AND UNLOADING VEHICLES 4 Sheets-Shem 3 Original FiledJuly 10, 1963 INVENTOR. ARTHUR SPIMANGER AND Roasszr V. BURT,

June 1, 1965 SPINANGER ETAL 3,186,568

METHOD FOR LOADING AND UNLOADING VEHICLES Original Filed July 10, 196340 47 J8 F1g.6 15

4 Sheets-Shem. 4

INVENTOR ARTHUR SPINANGER AND Rossar V. Bu er,

United States Patent 3,186,568 METHGD FOR LUADENG AND UNLQADENG VEHECLESArthur Spinanger and Robert V. Burt, Cincinnati, Uhio,

assignors to The Procter & Gamble Company, Cincinnati, Ghio, acorporation of Ohio Original application .luly 10, 1963, Ser. No.294,089. Divided and this application Nov. 2, 1364, Ser. No.

3 Qlaims. (Cl. 214-152) This is a division of application Serial No.294,080, filed July 10, 1963. The subject invention relates to a methodof loading and unloading vehicles intended to transport materials fromone location to another and, more particularly, to the loading andunloading of pre-assembled quantities of goods.

The presently used methods of loading vehicles (for example, highwayvans) are principally: (a) by hand or (b) by depositing pallet loads ofproduct in the van. Loading by hand presents several disadvantages.First of all, the material to be transported must be accumulated andcarried to the vehicle by means of pallets. Then the individual packagesof the material must be carried or transported by other means into thevan. Upon reaching the destination the packages must be carried out ofthe van and palletized and/ or assembled into units for furtherhandling. The foregoing involves substantial amounts of manpower andrequires the expenditure of considerable time, tying up both van andtruck dock at the loading and unloading points. This latter factaccounts for the necessity for warehouses to be designed so as toprovide a great many duplicate truck loading and unloading sites, acostly capital expenditure.

Loading by using pallets is expensive since the pallets must either bereturned or so constructed as to be expendable, and since such a systemrequires that ample truck space he left open for maneuvering the palletsinto position. Moreover, the pallets themselves occupy truck space whichmight otherwise be filled with product to be shipped. To date expendablepallets have not reached substantial commercial acceptance because ofrelatively high cost considerations.

Various other schemes for the loading and unloading of preassembledshipments have been proposed in the past, but these, too, werecommercially unacceptable due to equipment costs, inconvenience and,generally, to impracticality.

It is an object of the present invention to obviate the aboveditliculties.

Another object of the present invention is to provide a method by whichpreassembled quantities of goods to be shipped may be rapidly loaded andunloaded from vehicles, utilizing truly expendable means accompanyingsuch shipments and which may be adopted without incurwarehouse floor andvehicle bed; placing a material on the slide path to give the samehigh-slip characteristics;

positioning a flexible web-like sled on the slide path with its lengthparallel thereto and the coelli'cients of friction between the sled andthe path being less than that between the sled and the cargo to beloaded; placing the cargo on the sled leaving the ends thereofuncovered, the cargo being retained in place only by its weight; andpushing the loaded sled into the vehicle by means of a force acting onthe cargo at the end furtherm'ost removed from 3,ldh,5d8 Patented June1, 1965 ICC the vehicle, the force being directed parallel to the slidepath and causing both the cargo and sled to simultaneously slide alongthe slide path into position in the loading area of the vehicle.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as thepresent invention, it is believed that the invention will be betterunderstood from the following description taken in connection with theaccompanying drawings, in which:

FIGURE 1 is a perspective view of a warehouse loading dock and a highwayvan in loading position, with a unitized cargo placed in position withrespect to the balance of the elements comprising the apparatus used inpracticing this invention;

FIGURE 2 is a plan view of apparatus adapted to apply motive power forloading and unloading of cargo according to the present invention;

FIGURE 3 is a section taken along line 33 of FIGURE 2;

FIGURE 4 is a plan view of the loading operation in progress;

FIGURE 5 is a section taken along line 55 of FIGURE 4;

FIGURE 6 is a plan view of the unloading operation in progress;

FIGURE 7 is an enlarged fragmentary perspective view of the drawbarcombination employed in unloading ac cording to this invention;

FIGURE 8 is a section taken along line 88 of FIGURE 6;

FlGURE 9 is a partly broken fragmentary plan view of one construction ofa sled adapted for use in the present invention;

FIGURES 10 is an enlarged fragmentary view taken in cross sectionthrough the sled and dock runway of FIGURE 5;

FIGURE 11 is an enlarged fragmentary view in section of an alternativedock runway;

FIGURE 12 is an enlarged fragmentary sectional view taken through thesuperposed sled and van runway; and

FIGURE 13 is an enlarged fragmentary sectional view taken through thedockboard shown in FIGURES 1-5 and 8.

Referring to FIGURE 1, there is shown a preassembled load 15 comprisinga multiplicity of containers 16 stacked in interlocking engagement as isthe normal practice in preparing cargo for shipment. The placement andpositioning of the containers to can be accomplished by hand or bymechanical means, e.g., by means of clamp trucks, the operation anddetails of which are well known in the materials handling art. The load15 shown is in a compact state as would result from hand loading. Ifclamp trucks were used, the load would comprise two lengthwise rowsseparated sufficiently to permit operation of the clamp arms, or,alternatively, by using the method disclosed in the application for US.Letters Patent filed concurrently herewith by James M. Ewell andassigned to the assignee of the present invention.

If the preassembled load 15 is to be the only cargo loaded into highwayvan or trailer 1'7, thendesirably the load 15 will be approximately 82to 86 inches in Width, slightly less than about 40 feet long and of aheight variable in accordance with the density of the goods beingshipped. Generally speaking, over-the-road trailers or vans such as van17 have a bed area 96 to 92 /2 inches in width and 40 feet long.Consequently, when the preassembled load 15 is inserted in the van 17,it lacks about 7 inches of filling the van 1'7 in width and about 2 to 5inches in length.

The intended cargo, the preassembled load 15, is stacked upon a flexiblesled i8, desirably of width about '2 inches narrower than that of theload 15 and approximately 6 to 10 feet longer. Thus, the sled preferablyis about 80 to 84 inches wide and about 48 feet long. The load iscentered over the width of the sled 18 and the end of the load nearestthe van 17 is located close to the corresponding end of the sled 18.Such positioning leaves most of the uncovered length of the sled 18 onthe end thereof furthermost from the van 17 and available, as will laterbe made clear, for use in the subsequent unloading operation.

While the required strength of the sled material will vary in accordancewith the frictional and inertial forces encountered, it has been foundthat for preassembied loads of approximately 50,000 pounds and with thecoated runway materials hereinafter described, the tensile strength ofthe sled 13 should preferably be at least about 125 pounds per inch ofwidth. The material should also be thin and the flexibility such that itmay be formed into a compact roll which occupies relatively littlespace. These properties facilitate the rolled storage of sled materialprior to use and enable the sleds to be transported or returned to theshipper, taking up a minimum of space.

In addition to the flexibility and strength requirements, the sled 18should possess sufiicient wet strength to operate over the relativehumidity range that will be encountered. Moreover, the material shouldbe inexpensive and its other properties, for example, flexibility,should not change when exposed to normal extremities of climacticcondition.

FIGURES 9, 10 and l2show a sled 18 constructed of two sheets of kraftpaper 19 and 20 laminated in face-toface contact with reinforcing fibers21 running lengthwise therebetween. The reinforcing fibers may be jute,cottoo or any other suitable filament type of material. One suitablecombination of materials for such construction comprises two sheets ofkraft paper laminated together by a suitable adhesive and containing 2to 3 reinforcing fibers per inch of width. Where the reinforcing fibersare jute the composite sheet has a basis weight of approximately 190pounds per ream of 3000 square feet and a tensile strength of about 125pounds per inch of Width.

While the above describes a laminated filament rein forced sled, itshould be realized that any sheet or film material which fulfills thephysical requirements will be satisfactory and a laminated constructionis not essential. In this connection, a material such as Sorex 54936 (aheavy weight paper stock presently sold by Sorg Paper Co. and having abasis weight of approximately 200 pounds per ream of 3000 square feetand a tensile strength in the machine direction of 200 pounds per inchof width) has also been found satisfactory.

As shown in FIGURE 9, the sled 18 may be extrareinforced along itslongitudinal edges by means of spacing the fibers 21 more closely alongthe outer 3 or 4 inches of the sled 18 width. Such extra-reinforcing isdesirable in order to compensate for any minor misalignment of the loadfrom the direction of movement in the unloading operation, as will bemore fully understood from the balance of this specification.

Referring once more to FIGURE 1, the sled 18 in its unitizing positionoverlies a dock runway 22 having a top surface which in combination withthe lower face of sled 18 has coeflicients of static (fsd) and kinetic(or sliding) friction which are lower than the coeficient of staticfriction (fsl) between the bottom surfaces of containers 16 comprisingthe unitized load 15 and thetop or less than about .8 fsl) and fsd isless than approximately a As shown in FIGURE 10, the dock runway 22 cancomprise a floor overlay 23 madevof a row of exterior plywood panels orthe like, preferably fastened to the floor 24 of the warehouse by meansnot shown, the variations of which are well known in the art. Forexample, the overlay 23 may be adhered directly to the floor 24 by anadhesive such as epoxy cement or, alteruatively, could be secured to anetwork of lathwhich in turn is secured to the floor 24 by anchors,concrete nails or the like. The seams of the panels of materialcomprising the overlay 23 should be smooth and the contiguous edgesthereof made to match closely. The overlay 23 should be positioned inalignment with the truck loading position and in order to handle a fullvan 17 load should measure about inches wide. The length of the dockrunway and consequently, of the ovenlay 23 may be varied according tothe needs of the warehouse, terminating approximately 3 feet short ofthe edge of the warehouse loading dock.

Superposed over and secured to the floor overlay 23 is a film or sheet25. Thus, the overlay forms a foundation or base for the film or sheet.The film or sheet 25 must be durable (abrasion resistant), inexpensivein terms of cost per use and in combination with the lower surface ofthe sled 18 must have the low coefficient of static and kinetic frictionas described above. One suitable material may be plastic comprising highdensity polyethylene having a thickness of about A of an inch, which canbe stapled to the overlay 23, or, alternatively, bonded to the overlay23 by means of adhesives and an intermediate sheet of paper (thepolyethylene bonded to paper which in turn is bonded to the overlay 23).

It should be understood that many materials will be found to besatisfactory for use as the film or sheet 25 and the above describedmaterial is merely illustrative of the type contemplated for usein'connection with this invention.

An alternative construction for the dock runway is shown in FIGURE 11.This form of construction is well adapted for use in a warehouse havinga concrete floor. For the sake of clarity, the alternative dock runway22 is shown recessed in the floor, but it should be understood that suchrecessing is not essential to the operation of the loading or unloadingoperation.

As -Sl1OWn,the dock runway 22, comprises a smooth concrete surface 22acovered by a multiplicity of coats of plastic finish material. For.example, there may be coats 22b, 22c and 22d, all of which may be a onepart, oil-free moisture drying urethane varnish such as the urethanefloor varnish sold by E. I. du Pont de Nernours & Co., Inc. underthetrademark Imron. Alternatively, coat 22b may be a primer such as atwo part polyamide cured epoxy finish along with superposed coats 22cand 22d of either urethane varnish as de scribed above or a catalyzed 2part urethane enamel, such as Better Finishes & Coatings (30., Code No.91-02. Suitable primers are currently sold by The Glidden Co. as, NuponEpoxy and by E. I. du Pont de Nemours & Co., Inc. as Corlar Epoxy.Another alternative is to incorporate a silicone compound or powderedTeflon in the coat 22d. 7 I a If an existing rough warehouse floor isbeing adapted for use in forming a dock runway22', the smooth surface22a' may he produced by means of the well known terrazzo grindingprocess. Frequently, deep grease penetration will be encountered inolder warehouses and it will be necessary to etch the smooth'surfacewith muriatic acid 'in order to assure good bonding of the coat 22b.

Abutting .the outer end of the dock runway 22 and functioning as anextension thereof interconnecting the dock with the van 17 is adockboard 26 The proximal end 27 as shown in FIGURE 4 of the 'dockboard26 is pivotally mounted on lugs, not shown, secured to the warehousefloor 24 and is flush and fits closely to the adjacent end of the runway22 .or'22'. To compensate for variations in the. height. of the bedv 29of the van'l7,

eneases the distal end 28 of the dockboard is turned down as shown inFIGURES and 8.

Preferably, the dockboard is approximately as wide as the preassembledload and about 3% feet long, extending a few inches into the van 17.While the dockboard 26 may be constructed of any suitable rigidmaterial, it is thought advantageous to use A1" thick magnesium plate.The upper surface of the dockboard 26 is covered with a materialdesigned to provide a continuity of the low coefficient of static andsliding friction with the lower surface of sled 13. As disclosed inFIGURE 13 the material may comprise two coats of plastic finish. Onesuitable upper dockboard surface has been prepared by using a coat 26aof vinyl wash primer such as the Sherwin Williams Co. Grip Clad primerand then applying a coat 26b of urethane varnish or enamel as describedpreviously in connection with dock runway 22.

A pair of oppositely disposed arcuately formed vertical guides and 31are pivotally mounted on pipes anchored in the warehouse floor 24. Theguides 39 and 31 are mounted on either side of the dockboard 26 and aswill be understood by reference to FIGURES 1, 4 and 6 are positioned tofunnel smoothly the load 15 into the van 17 during the loadingoperation. The armate configuration of the vertical guides 30 and 31 notonly places the inner ends 36a and 31a thereof in position to commencethe funneling action, but in addition compensates for off-centerplacement of the van 1'7 without excessively reducing the van 17 widthavailable for loading. In this connection, if the vertical guides 36 and31 were planar, then off-center placement of the van 17 would cause theouter end of one of the guides to extend substantially further away fromits respective side of the van 17 than would be the case with theillustrated arcuate construction, thereby reducing the effective load-'ing width of the van 17.

Preferably, the inner surface of each of the vertical guides 30 and 31is smooth, and may, if desired, be covered with a material similar tothat used for film or sheet 25 or coated with a plastic finish materialas discussed hereinabove with respect to coatings for alternative dockrunway 22.

As shown most clearly in FIGURES 5 and 8, a vehicle or van runway 32overlies the bed 29 of the van 17. The van runway 32 should coversubstantially all of the cargo loading area of the van 17 and preferablycomprises a single sheet having dimensions approximating that of the van17 bed, although two or more overlapping sheets extending the fulllength of the van 17 have been found satisfactory. While the van runway32 can be affixed to the bed 29 of van 17, such is unnecessary in mostcases and in the interest of economy should be left loosely in position.

The van runway 32 is a thin, flexible web having a highslip or lowfriction upper surface and preferably a substantially less slipperylower surface. In the case of the van runway 32, it is important thatthe coefiicients of static and kinetic friction between the bottomsurface thereof and the bed 29 of van 17 be higher than that between theupper surface of the van runway 32 and the lower surface of the sled 13.Here, too, a ratio of at least about 1.25:1 is desirable.

One suitable material for the van runway 32 is shown in FIGURE 12,comprising a kraft paper 33 having a basis weight of about 70 to 90pounds per ream of 3000 square feet, the upper surface of which has beencoated with a 1 mil thick; layer 34 of low density polyethylene, such asUS. Industrial Chemicals Polycoating formulation 203-49. In combinationwith the filament reinforced sled described above, such a van runway hasa coefficient of static friction of about .10 and a coefiicient ofkinetic or sliding friction of approximately .09, both of which are verysatisfactory in view of the coefficient of static friction of about.25.30 between the average van bed 2% and the kraft side of the runway32.

- one device capable of performing the function.

Another suitable van runway material is a glassine paper having a basisweight of about pounds per ream of 3000 square feet, the upper surfaceof which is coated with a 1 mil thick layer of silicone, for example,Dow #22 silicone. In addition to the above, it is feasible to constructsuch a runway of a 90 pound kraft paper coated on one side with a 1 millayer of Tenite, a thermoplastic made from a cellulose ester (e.g.,cellulose acetate or cellulose acetate butyrate).

The van runway 32 material is maintained in roll form in the warehouseon a portable roll holder (not shown) and the van runway 32 may be cutto length according to the length of the van 17. It is necessary, asshown in FIGURES 5 and 8, that the rear edge of the van runway 32 beoverlapped by the distal end 23 of the dockboard 26 during the loadingoperation.

Apparatus for supplying motive power is generally indicated by referencenumeral 35. While many devices may be used for such an application, onepreferred embodirnent is illustrated in FIGURES 2 and 3 as comprising anelectrically powered, motor driven Windlass 36, the drum 37 of which isoriented vertically so as to pay out a cable loop 38 horizontally andbelow the surface of the dock runway 22 or 22'. The loop 38 is held intension by idler pulley 39 located in a recess in the dock beneath thedockboard 26. Two cable troughs extend between the Windlass 36 and thepulley 39, each carrying one leg of the loop 38 and extendingsubstantially parallel to the length of the dock runway 22. One of thecable troughs is substantially centered along the runway 22 and therunway is slotted to provide continuous access to the leg of the loop 33passing therethrough. If necessary, the dock board 26 is also slotted,as shown in the various figures.

A wheel-equipped movable bulkhead 46 is fastened by means of clamp 41 tothe leg of the loop 38 passing through the centered and open trough andthereby propelled in one direction or the other along the dock runway 22or 22', according to the direction of rotation of the drum 37. Lying toeither side of the clamp 41 are guide wheels 41a and 4111 which ride onthe internal surfaces of the centered trough, thus enabling the troughto act as a guideway for the bulkhead 49. In this manner the front face44 of the bulkhead is maintained perpendicular to the length of therunway 22 throughout the limits of its travels. The driving connectionbetween the motor 42 and the Windlass drum 37 and the reversingmechanism therefor are not shown, but the design of such elements arewell within the skill of those of ordinary slrill in the art and couldcomprise a reversible gear box unit.

The bulkhead 40 is equipped on either side with internally threaded boltholes 43, as shown in FIGURE 1, the purpose of which wiil be laterclarified. The front face 4 of the bulkhead is approximately the samesize as the width and height of the unitized load 15, being essentiallyflat and smooth. For best operation it is preferred that the face 44 beslanted forwardly slightly so that the top edge thereof is advancedapproximately one inch over a 63 inch height.

While a great deal more could be said about the construction of theapparatus for supplying the motive power,

such details do not play a part in the present invention and it isbelieved that the brief description above suffices to explain thegeneral principles and mode of operation of Other details and evenalternative means of providing motive power are well within thecapabilities of those of ordinary skill in the art.

In use, the cooperation of the above described elements and the-methodby which loading and unloading of preas semble-d loads is accomplishedwill now be described. Firstof all, a sled 18 of the correct length forthe load 1.5 is obtained, for example, by separation of the same from aroll of sled material. Then the sled I8 is laid flat on the docl; runway22, parallel thereto. It will be noted that at this time the movablebulkhead 40 is in in its innermost position.

so as to curl upwardly from the runway 22 as shown in FIGURES 1 and 5.Next, the load 15 is assembled, as described previously, on top of thesled, extending slightly outwardly therefrom about an inch on eitherside and positioned on the forward end thereof.

The van 17 may be placed in loading position at any time and should becentered as closely as possible with the dockboard 26 which is in itsraised position on its hinge; The vertical guides are both pivotedinwardly so that the outer ends thereof are close together, within theconfines of the loading dock. In its loading position the van 17,dockboard 26 and dock runway 22 are parallel and in close alignment. Nospecial treatment of the van bed 29 is needed except that it is sweptout to removeloose debris. In this connection, any truck acceptable forhand loaded cargo is acceptable for use with the present invention.

With the dockboard 26 still in its raised position, a van runway 32 ofthe correct length for the van 17 is cut from a supply of van runwaymaterial. The van runway 32 is placed loosely in the van 17 over thecargo,

receiving area of the bed 29, with the coated side uppermost. Then thevertical guides are swung outwardly until their outer ends contact therespective inner side walls of the van 17 and the dockboard 26 islowered so that the distal end 28 thereof rests upon the van runway'load 15 thereon to slide along the sliding pathway com-. prising thedock runway 22, dockboard 26 and van run-- way 32, without shifting theload 15 on the sled 18 or moving the van runway 32 from its position onthe bed 29 of the van 17. Since the elements comprising the slidingpathway are presumably in direct alignment with the load 15, the loadingoperation proceeds without incident,

being terminated by stopping the forward movement of the bulkhead 40when the load 15 rests wholly within the cargo loading area of the van17. misalignment in that the van 17 is not centered with the runway 22or 22', then one of the vertical guides will contact the correspondingside of the load '15, tunneling the sled supported cargo into the cargoreceiving area of the van 17.

Then the windlass direction is reversed to move the bulkhead 49 to itsinnermost position, away from the van 17. Finally, the dockboard 26 ispivoted to its raised position and the vertical guides swung inwardly,out of the van interior, and the van 17 is ready to be transported toits destination. The whole loading operation described generally takes amatter of minutes whereas the prior art methods described previouslyoccasionally take several hours. It will be noted that load 15 stillrests on sled 18 and that, in turn, is superposed over van runway 32,both of which are expendable and available for use 7 in the unloadingoperation hereinafter described.

When the van 17 is positioned at the unloading dock at its destinationthe unloading operation may commence. The unloading station is desirablyof the same construction as the loading station previously described,i.e., with a motive power apparatus 35, clock runway 22 or 22' anddockboard 26. No vertical guides 30 and 31 are needed for the unloadingoperation but if provided at a combined loading-unloading station, willnot interfere with the load 15 transfer. in such a case the verticalguides 30 and 31 If there is a tendency for the sled 18 to curl,preferably the sled 18 should be positioned.

If there is some:

may be placed as they were during the loading operation or,alternatively, each rotated 180 to completely remove themfrom theintended path ofvunloading.

The unloading operation and the apparatus used therefore are shown mostspecifically in FIGURES 6, 7 and 8. FIGURE 7 illustrates theconstruction of a preferred embodiment of a drawbar 45 used to apply apulling force uniformly across the width of the sled 18. A 5 inch squarelow carbon steel tube having inch thick walls and a length of about 86inches has proven satisfactory. While the specific design of the drawbarmay be varied according to the preference of the user, it is essentialthat under the conditions of use the drawbar should not deflectsufiiciently to create an imbalance of tension across the sled 13 whichcould result in portions thereof being loaded in excess of its ultimatetensile strength, thereby causing the sled 18 to rupture. There areprovided at each end of a pair of opposed sides of the drawbar 45 holesor apertures 46 of sufficient size to accept the threaded angularlydisposed end of pull bars. 47

The two pull bars 47, one of which is also depicted in FIGURE 7, aresubstantially identical and comprise /3 inch diameter rods of low carbonsteel, one end there of being threaded and bent upwardly so as to form a90 angle with the central portion thereof. The other end is flattened inthe same plane as that including the upwardly bend end and has a boltclearance hole drilled throughiit for connection .to the bulkhead 40.

The first step of the unloading operation is to secure the sled 18 tothe drawbar 45. While clamps, etc. could perform this function, thepreferred means is by smoothly wrapping the unloaded rearward end of thesled 18 two complete turns around the drawbar 45. In its wrappedposition the drawbar 45 is substantially perpendicular. to the length ofthe sled 18. 7

Next, the upwardly bent end of a pull bar 47 is inserted through each ofthe oppositely disposed apertures 46, and a nut used to hold it inposition, as illustrated in FIGURE 7. Then the bulkhead 40 is broughtadjacent to the drawbar 45 and its position adjusted in or'out byinching movements, until the bolt clearance hole at'the other end ofeach of the pull bars 47' is linedup with the bolt holes 43 on therespective sides of the bulkhead 40, as shown in FIGURES 5 and 8. Atthis point a bolt 43a may be inserted through each bolt clearance'holeand screwed into firm engagement with, the, threads of the correspondingbolt hole 43. The bulkhead 40 is then moved smoothly away from the van17, the attached drawbar 45 pulling the sled 18'with the load 15 thereonup the dockboard 26 and alongthe dock runway 22 and 22, to the positiondesired, the sliding movements being permitted by virtue of thecoefficients of static and kinetic friction previously described. Thevan runway 32 remains in position on the bed 29 of the van 17 and may bereused in loading the van, if undamaged.

Following the above, the pull bars 47 are removed from attachment to thebulkhead 4i) and from engagement within the apertures in the drawbar 45.Then the drawbar 45 is unwound from the sled 18 and the load dispatchedto other locations as desired. The sled 18 may also be reused ifundamaged, and it has been found that the average number of uses of suchsleds is about five.

If the destination has no prepared unloading station such .as describedabove, it is still possible to utilize the sled-slide path principledescribed above. In this case, however, the van runway would initiallybe cut to a length sufficient not only to cover the length of the van17, but also to form a slide path extending intothe receiving Warehouse.During the loading operation the dockboard 26 would cover the materialin excess of the-van 17 length. After loading, the excess ,van runwaymaterial would be rolled'up and placed within the van 17 and transportedwith the load 15; Later, at the unloading destination the excessmaterial would be unrolled'up over the do-ckboard of the receivingwarehouse and across the floor thereof to an unloading position.Thereafter, the unloading operation would proceed as described above,utilizing any form of apparatus available to apply the pulling force.For example, a heavy fork lift truck could be used to tow some loadsfrom the van 17.

Thus, it will be seen that there is provided an economical method toaccomplish the loading and unloading of unitized loads in vehicles fortransport. Such method substantially reduces the waiting time ofvehicles at both loading and unloading docks and is capable ofmaterially reducing the handling of the cargo during shipment.

Many modifications of the above invention may be made and it is notintended to hereby limit it to use with the particular embodiments shownor described. For example, it would be possible to pull, as well aspush, the load into the van. The terms used in describing the inventionare used in their descriptive sense and not as terms of limitation, itbeing intended that all equivalents thereof be included within the scopeof the appended claims.

What is claimed is:

1. The method of loading a vehicle at a warehouse clock, which methodcomprises:

(A) providing a slide path extending from a unitizing area into theloading area of said vehicle, said slide path comprising continuousportions of the surface of the warehouse floor and vehicle bed,

(B) placing a material on said slide path so as to present a surfacethereon having high-slip characteristics,

(C) positioning a thin flexible web-like sled on said slide path at theunitizing area with the length of the sled parallel to the length ofsaid slide path, the coeificient of static and kinetic friction betweensaid sled and the surface of said slide path being less than thecoeflicient of static friction between the sled and the cargo to beloaded,

(D) placing the cargo in a substantially compact mass on said sled,leaving the ends of said sled uncovered, the sole means of securement ofthe cargo to the sled being effected by the weight of the cargo and thesaid coeflicient of static friction between the sled and the cargo, and

(E) pushing the loaded sled into the vehicle by means of a pushing forceacting directly on said cargo at the end thereof furthermost removedfrom said vehicle, said pushing force being directed parallel to saidslide path and causing said cargo and sled to simultaneously slide alongsaid slide path into position in the loading area of said vehicle.

2. The method of interwarehouse shipping of a unitized cargo in avehicle, which method comprises:

(A) providing a slide path from a unitizing area in a warehouse into theloading area of said vehicle, said slide path comprising continuousportions of the surface of the warehouse floor and vehicle bed,

(B) placinga material onsaid slide path so as to present a surfacethereon having high-slip characteristics,

(C) positioning a thin flexible web-like sled on said slide path at theunitizing area,

(D) placing the cargo in a substantially compact mass on said sled,leaving at least one end thereof uncovered, said cargo being held inplace on said sled only by means of frictional forces effected by theweight of the cargo resting on the sled,

(E) moving the loaded sled into the vehicle with the said uncovered oneend of the sled positioned at the vehicle end from which unloading is tooccur, said moving being accomplished by a force acting directly on theload at the end thereof furthermost removed from said vehicle,

(P) transporting the vehicle to the shipping destination and placing thevehicle unloading end in alignment with a slide path leading to anunloading position, and

(G) removing the loaded sled from said vehicle by means of a pullingforce applied to the said uncovered end of said sled to thereby slidethe loaded sled to said unloading position.

3. The method of transporting a unitized load in a vehicle from aloading dock to an unloading dock at the destination, which methodcomprises:

(A) providing a slide path terminating within the loading area of saidvehicle, said slide path comprising continuous portions of the surfacesof the loading dock and vehicle bed,

(B) placing a material on said slide path so as to present a high-slipsurface having a lower coefiicient of sliding friction than originallypossessed by the surfaces comprising said slide path,

(C) placing a thin flexible web-like sled on said slide path with thelength of the sled parallel to the length of the slide path, thecoefficients of static and kinetic friction between the sled and thehigh-slip surface being less than the coefiicient of static frictionbetween the sled and the load to be carried thereon;

(D) placing the load in a substantially compact mass on said sled, theload being secured thereto solely by frictional resistance to relativemovement, said web having at least one end thereof which is not coveredby the load,

(E) moving said loaded sled into said vehicle with the uncovered end ofthe sled positioned at the vehicle end from which unloading is to occur,said moving being accomplished by means of a pushing force actingdirectly on and substantially uniformly across the width of said load atthe end thereof furthermost removed from said vehicle,

(F) transporting the said vehicle to the unloading dock at the shippingdestination and placing the vehicle unloading end in alignment with aslide path extending to an unloading position and,

(G) removing the unitized load by application of a pulling force applieduniformly across a substantial portion of the load-bearing width of saidone end of the sled to thereby slide the loaded sled to said unloadingposition.

References Cited by the Examiner UNITED STATES PATENTS 2,422,910 6/47Katinos 214-38 2,711,835 6/55 Kappen 214-38 3,040,914 6/62 Johnson eta1. 21438 3,081,886 3/63 Flexman et al. 214-l HUGO O. SCHULZ, PrimaryExaminer.

1. THE METHOD OF LOADING A VEHICLE AT A WAREHOUSE DOCK, WHICH METHODCOMPRISES: (A) PROVIDING A SLIDE PATH EXTENDING FROM A UNITIZING AREAINTO THE LOADING AREA OF SAID VEHICLE, SAID SLIDE PATH COMPRISINGCONTINUOUS PORTIONS OF THE SURFACE OF THE WAREHOUSE FLOOR AND VEHICLEBED, (B) PLACING A MATERIAL ON SAID SLIDE PATH SO AS TO PRESENT SURFACETHEREON HAVING HIGH-SLIP CHARACTERISTICS, (C) POSITIONING A THINFLEXIBLE WEB-LIKE SLED ON SAID SLIDE PATH AT THE UNITIZING AREA WITH THELENGTH OF THE SLED PARALLEL TO THE LENGTH OF SAID SLIDE PATH, THECOEFFICIENT OF STATIC AND KINETIC FRICTION BETWEEN SAID SLED AND THESURFACE OF SAID SLIDE PATH BEING LESS THAN THE COEFFICIENT OF STATICFRICTION BETWEEN THE SLED AND THE CARGO TO BE LOADED, (D) PLACING THECARGO IN A SUBSTANTIALLY COMPACT MASS ON SAID SLED, LEAVING THE ENDS OFSAID SLED UNCOVERED, THE SOLE MEANS OF SECUREMENT OF THE CARGO TO THESLED BEING EFFECTED BY THE WEIGHT OF THE CARGO AND THE SAID COEFFICIENTOF STATIC FRICTION BETWEEN THE SLED AND THE CARGO, AND (E) PUSHING THELOADED SLED INTO THE VEHICLE BY MEANS OF A PUSHING FORCE ACTING DIRECTLYON SAID CARGO AT THE END THEREOF FURTHERMOST REMOVED FROM SAID VEHICLE,SAID PUSHING FORCE BEING DIRECTED PARALLEL TO SAID SLIDE PATH ANDCAUSING SAID CARGO AND SLED TO SIMULTANEOUSLY SLIDE ALONG SAID SLIDEPATH INTO POSITION IN THE LOADING AREA OF SAID VEHICLE.